1. Field of the Invention
The present invention relates to the art of electrophotographic recording systems, and more particularly to a color image recording apparatus for successively forming electrostatic latent images on a recording medium with information provided by electronic signals, and successively developing the electrostatic latent images, with a plurality of respective color image developing units, into respective visible component color images, which are superimposed into a composite color image on the recording medium.
2. Description of Related Art
As color plotter systems and printers are developed in recent years, there is a demand for printed color images of as good quality as color photoprints.
Conventional color image recording systems include monochromatic electrophotographic image recording systems and multicolor electrophotographic image recording systems. In the monochromatic electrophotographic image recording systems, electrostatic latent images are developed into visible images immediately after the latent images are formed. In the multicolor electrophotographic image recording systems, since two or more latent images of different colors are formed and developed in superimposed relation on a recording medium, the recording medium is reciprocally moved a plurality of times while repeating the formation and development of the electrostatic latent images until a composite color image is produced.
One multicolor electrographic image recording apparatus is disclosed in U.S. Pat. No. 4,569,584 patented Feb. 11, 1986. The disclosed color image recording apparatus includes a recording station having a recording electrode means for forming a latent image on a recording medium, and a linear array of independent developing means adjacent to either one side or both sides of the recording station.
In operation, the recording medium is fed in one direction while a first component latent image is being formed on the latent image. Thereafter, the first component latent image is developed into a first component color image. Then, the transport of the recording medium is reversed, and a second component latent image is formed in superimposed relation to the first developed image, followed by its color development. The above process is repeated until all component latent images are formed and developed to form a desired composite color image.
Japanese Laid-Open Patent Publication No. 63(1988)-149664 published June 22, 1988 shows a similar multicolor image recording apparatus. The disclosed multicolor image recording apparatus also has a recording medium reciprocally movable a plurality of times to repeat the formation and development of a plurality of electrostatic latent images until a composite color image is produced. However, unlike the image recording apparatus disclosed in U.S. Pat. No. 4,569,584, a plurality of developing units are mounted on a rotor, and are selectively brought into a developing position by rotation of the rotor. The developing units on the rotor take a less space than the linear array of developing means, and the image recording apparatus may be smaller, than the image recording apparatus with the linear array of developing means. In addition, positional control of the developing units on the rotor is easier to perform.
When the recording medium is wound back, however, any developing solution left in a groove of the developing unit tends to be applied to the recording medium, resulting in smears in the plotted image area. Such smears are caused because though the developing units are spaced a certain distance from the recording medium as it is wound back, any residual developing solution is apt to be applied to the recording medium due to the surface tension of the residual developing solution in the developing units, and the recording medium rubs against the recording head.
Another problem with the rotary image developing system is that when the developing units are not in the developing position, any residual developing solution tends to flow or drop out of the developing units, causing contamination on surroundings with toner particles contained in the leaking developing solution.